I think the timeless and agless appeal belongs to the magic of disney .. Whenever I pop a dvd in and see the disney logo and the works, you feel like a kid again, you can relive some childhood memories, even with the newest releases, There's a magic to watching it... for a few hours, you can be 10 again and let the worries of the world be forgotten...
I too find the cliche that animation is just for kids laughable.. I would go out on a limb and say that 80% of the animation created today is geared towards adults, Anime is 100% adult oriented, Family Guy, Futurama, King of the hill, Ren and Stimpy.. all adult oriented.
But there's a special appeal to Garfiend and Heathcliffe, Mighty Mouse, Tom and Jerry, Super Friends, etc etc.. Child oriented in nature, easily enjoyed as an adult as well.
In closing

Good animation has no age demographic nor needs one associated with it. If you like it, watch it, if others make fun of you for it, they are losing out on one of life's last true simple pleasures.
Good day... godspeed.. Lightyear..signing off the soapbox..